Field of the Invention
The present invention relates to a rack bar unit of a vehicle steering device, and more particularly, to a rack bar unit of a vehicle steering device, in which a rack gear made of carbon steel is coupled to a rack bar body made of magnesium.
Description of the Related Art
In general, a vehicle steering device as a device for a driver to arbitrarily steer a driving direction of a vehicle includes a steering operating mechanism including a steering handle directly operated by the driver and a steering column integrally connected with the steering handle and rotatably supporting the steering handle while rotating together with the steering handle, a steering gear box installed in link with the steering column and receiving a rotary motion of the steering column and converting the received rotary motion into a horizontal linear motion, and a steering link mechanism interlockedly coupled to the steering gear box and connected to a vehicle wheel and thus transferring the horizontal linear motion of the steering gear box to the vehicle wheel to steer the vehicle wheel.
The steering gear box includes a pinion gear which rotates by receiving operating force of the steering handle of the driver and a rack bar including a rack gear which engages with the pinion gear and converts the rotary motion of the pinion gear into the horizontal linear motion.
FIG. 1 illustrates one example of a steering gear box and a steering link mechanism in the related art.
A steering gear box 10 includes a rack bar 12 deployed to extend in the width direction of a vehicle and a pinion gear 14 which engages with the rack bar 12 and connected with a steering handle (not illustrated) to receive operating force of a steering handle of a driver and horizontally linearly move the rack bar 12.
The steering link mechanism 20 includes a tie rod 22 interlockedly connected to an end of the rack bar 12 and a tie rod end 26 interlockedly connected to an end of the tie rod 22 and mounted with a ball joint 24.
A wheel bearing 30 is mounted on a vehicle wheel in order to rotatably support the vehicle wheel, a knuckle 40 is fastened to the wheel bearing 30 in order to steer the vehicle wheel, and the knuckle 40 is interlockedly connected to the tie rod end 26 through the ball joint 24.
As a result, when the driver operates the steering handle, an operating motion of the steering handle is transferred to the pinion gear 14 through the steering column to rotate the pinion gear 14, the rotary motion of the pinion gear 14 horizontally linearly moves the rack bar 12, and the horizontal linear motion of the rack bar 12 is transferred to the vehicle wheel via the knuckle 40 through the tie rod 22 and the tie rod end 26 to steer the vehicle wheel in an intended direction of the driver.
Since the steering device in the related art is a primary component directly connected with safety of the driver and a vehicle passenger, the steering device is manufactured with sufficient strength so that damage of the component is minimized even under a worst situation, and as a result, in particular, a diameter of the rack bar is designed to be large in order to improve the strength of the rack bar.
However, when the diameter of the rack bar increases, a total weight of the steering device increases while the sizes of components associated with the rack bar also increase, and as a result, weight and manufacturing cost of the vehicle increase and a steering operating sense also deteriorates while steering.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.